In the Beat of a Heart
by Cobrilee
Summary: It takes five years for Derek to come home, but when he does, he realizes that was five years too long. Things have changed in his absence, things like the hardness in Stiles' eyes and the bitterness in his voice, and Derek wishes he'd been there to stop it. Regrets fix nothing. But maybe taking a place at his side will.


**A/N: This was written at like one in the morning and is unbeta'ed, so I apologize for any mistakes I missed. Based off a Tumblr post including a lot of GIFs of Stiles whaling on people in season five, which, I'm not ashamed to say, turns me on greatly. Thus this fic was born. Warnings: Includes a brief description of mostly-canon-typical violence, and top Stiles/bottom Derek, which I know some people don't care for. This is not a happy fic, but it is hopeful. (Oh, and also because I know a lot of Sterek fans flip out over her, Malia is mentioned twice, but there is zero hint that there is anything between her and Stiles. Even their past canon relationship is never referred to.)**

"Your heart didn't miss a beat."

Stiles doesn't respond to the observation at first, and it gives Derek a moment to study him. To really and truly look at this man-because he's no longer a little boy-and see the changes that he missed while he was gone. His eyes roam over the long, loose limbs that were once gangly and flailing and are now controlled, measured in their movements. Lethal. He watches the eyes that have settled into something cool, suspicious, sharp and analytical, instead of the wide, mostly-innocent pools of whiskey and honey they used to be. He's no longer skinny, no longer defenseless, and Derek wonders if he's no longer _Stiles._

Finally, after a silence that once would have been considered awkward and is now simply anticipatory, Stiles huffs out a breath in acknowledgment. "What are you talking about?"

It takes Derek a second to halt his character study and recall the statement he'd made. "When you were fighting." _When you were killing._ "Your heart didn't miss a beat."

Shrugging laconically, Stiles reaches past him and opens his fridge, pulling out a bottle of water and tilting it up to his lips, tipping his head back and swallowing deeply. Derek watches the way his throat constricts with each swallow and has to fight back the urge to do so himself. "I protect what's mine."

"Am I yours, then?" The words are out before he can help them, but Stiles had gone on the attack tonight to defend Derek. Had torn into the creatures, whatever they had been, without hesitation. Gone were the days of the baseball bat; now he wielded a wicked-looking blade that rivaled Kira's. He'd known how to use it, too, swinging it with deadly precision and accuracy. By the time Derek had recovered from nearly having his arm ripped off and a stiletto knife rammed into his thigh, Stiles had efficiently dispatched all but two of the team of six. Derek had leaped into the melee and viciously ripped off the head of one of the remaining two while Stiles gutted the last, ripping upward from belly to neck with a grotesque squelching noise.

When they had stepped back, both breathing harshly and covered in blood and gore, Stiles' heart was beating rapidly from the exertion, but there was no hitch in it, no stutter or tremble. There hadn't been, not once, the entire time they were fighting. Derek would be lying if he said the sheer determination of will on Stiles' face, his steadiness and competence in the face of the attack, didn't do something to him. That something was resulting in his pants tightening and his own heart racing from more than the thrill of battle and coming out victorious.

His words bring a slow, spreading smirk to Stiles' face, one that had thinned from boyish roundness into sculpted, hardened lines, and Derek once again feels the need to swallow past a dry throat. "I don't know, Derek. What do you think?"

"You haven't seen me in five years. You have no reason to think of me as yours."

Stiles slouches against the kitchen counter, draining the last drops from the bottle of water and tossing it carelessly into the sink. Derek doesn't even flinch against the harsh clang of the plastic shell against the dishes sitting there. "Maybe. But you were mine once. Just like all of you were."

Derek doesn't miss the past tense. Most everyone has left; they moved on to bigger and better things, got the hell out of Beacon Hills as soon as their sentence was up, never looking back. Derek knows Stiles, Liam, and Malia are all that are left. Stiles because he couldn't abandon his town, Liam because he needed a leader and Scott had made it clear it wouldn't be him, and Malia because she had nowhere else she'd rather be. They made for an odd little pack; a human, a beta, and a werecoyote, but Malia had updated him often enough that he knew somehow, they worked.

"I haven't been yours in a long time," Derek says, his voice whisper-soft, and Stiles smiles even further, but there's no happiness in it. It's a look that makes it seem as if _Derek_ is the naïve and innocent one, and Stiles is the world-weary soldier. In a way, he is. He's stayed behind in the hell that everyone else, including himself, was so desperate to escape that they left behind every casualty in a bid for their own sanity. He took on the job that no one else wanted because it wasn't in his nature to give it away.

"Let's be real, Derek. You were never _truly_ mine," Stiles answers in amusement, and his words are like little bee stings across the back of Derek's neck. "You were always on this little island with the sign that said 'look but don't touch'."

"Is that where you got the sign for yours?" Derek retorts. "Because you're just as emotionally detached as I ever was. Maybe even more so, because for as broken as I always was, I was never brittle."

The laughter comes quickly, a sharp crack devoid of mirth, and this time Derek _does_ flinch. "Come on, Derek. You of all people know what this life does to you. It strips you of everything. What's left but the empty shell, going through the motions?"

Derek aches; this isn't what he wanted for Stiles. It isn't what he wanted for any of them, but to see the once bright-eyed young boy so full of optimism and humor now reduced to this-it rips at him. "You know that's not true. If you were just going through the motions, you'd have stopped a long time ago. You do this because you care. Because someone has to."

Stiles shrugs again; the gesture noncommittal and telling him nothing. "Think whatever you want, Derek. But you're right about one thing. Someone has to. We're the someones."

The resignation in his face and voice are what nearly do him in. This can't be his Stiles. This can't be all that's left. "I've missed so much. You've changed so much and I missed all of it."

Stiles' eyes brighten as a small, sly smile ghosts across his face. "You want to know what else has changed? I'm not afraid to do this anymore." He crosses the small space between them, his fingers wrapping firmly around the back of Derek's neck, and pulls him in. When their lips meet Derek puts up a show of resistance-Stiles clearly isn't in the right frame of mind mentally to engage in this-but Stiles dismisses it impatiently and slides his other arm around Derek's waist, holding their hips tightly together. Derek knows he could easily break the hold, Stiles' newfound competence notwithstanding; he _is_ a werewolf after all. Strangely, he doesn't want to. This is a new Stiles, an adult who knows what he wants and isn't afraid to ask for it-fuck, to _take_ it. He also knows if he were to break away, Stiles would let him go. That alone makes him not want to break away.

Derek finally responds, slotting his lips against Stiles' and parting them with his tongue, and Stiles makes a noise of triumph into his mouth. Derek grumbles, although it's less irritated than he would like, and Stiles responds by fisting his hair-still wet from the showers they'd taken after getting back to Stiles' tiny apartment, battered and sore and covered in blood-and angling Derek's head a little more, deepening the kiss. It's frantic, possessive, not the sweet, unhurried thing Derek had been imagining for years. It doesn't matter. It's better. It's _real,_ and that's something Derek has never let himself believe would happen.

"My room," Stiles grunts as he pulls away, and Derek can't do anything but nod. At this point he's ready to just bend over the couch because the idea of making it to the bedroom is incomprehensible. Make it they do, however, and Stiles wastes no time in stripping his clothes off, the movements efficient and in control, and Derek can't remember the last time he got this hard, this quickly. A quick grin flashes over Stiles' face as he clearly notices-the thin cotton of the pajama bottoms Stiles lent him mold to his cock and hide nothing-but then it's gone as Stiles stalks toward him. "You're still dressed. Come on, Derek, time's wasting."

The words spur him on, and he's hurriedly shedding the wife beater and bottoms until he's standing in front of Stiles, completely nude and achingly hard. Stiles eyes him with appreciation, eyes gleaming, and sinks to his knees. Derek can do nothing but wind his fingers through Stiles' hair and clutch at the back of his head as Stiles takes him in with one practiced swallow. It's already abundantly clear that this is not going to be some slow, languid love-making session, but Stiles doesn't hesitate in setting a demanding pace, and Derek is surprisingly okay with that. They'll have that slow, languid moment later. He's determined not to miss out on it.

A guttural groan is torn from his throat when Stiles fists the length that can't fit into his mouth, not that there's much. Stiles is swallowing him, the head of his cock bumping the back of his throat, and Derek feels a low whine curling up and escaping his mouth. "Jesus," he rasps, tugging on Stiles' hair. "When the fuck did you get so good at deep-throating?"

Stiles hums as an answer, and Derek has to physically hold back from yanking on his hair so hard he chokes him. Stiles' mouth is wet, his tongue demanding, his strokes sure and determined, and Derek is perilously close to falling over the precipice. Saliva drips from the corners of his lips and Derek's dick feels like it's simultaneously in a warm bath and stuck in a pool jet, all wet heat and pressure and suction and fuck, fuck, he's going to-.

"Stiles!" he gasps out, pulling away before he unloads his release down Stiles' throat. "Stop." Stiles does, lips turning down in a pout, and God, that's going to be his undoing. "I don't want to come yet."

"Why? Think you won't be able to get it up again?" The taunt falls easily from Stiles' lips as he grins impishly, and there, that's what Derek wants to see. A hint that the old Stiles, the Stiles he'd loved so much it nearly killed him to walk away, was still there. Under everything, under the bitterness and the disillusionment, the man who's haunted his memories every day for five years still exists.

"I want you," Derek says, instead of taking the bait. He waits to see if Stiles gets it.

He does. "I'm going to fuck you," Stiles says simply, and it's exactly what Derek wants. As Stiles steps away to rummage through his night stand, Derek lays out on the bed. He's not exactly sure what Stiles wants, but he's willing to take direction. The control isn't something he gives up very often, but something tells him Stiles needs this.

Once Stiles has found the lube he slides the drawer shut with a snap and climbs onto the bed, situating himself between Derek's spread thighs. He's as efficient with slicking up his flushed, leaking cock as he was with stripping out of his clothes, and Derek wishes for a moment they could slow it down. He wants to taste Stiles, feel the weight of his dick on his tongue and the girth fucking into his mouth, and this is all going much faster than he wants it to.

He reminds himself that he's going to make sure this isn't the last time, and allows himself to fall under Stiles' spell once more. "No condom?" he asks, and Stiles smirks at him.

"You're a werewolf. I'm safe. What, you don't like barebacking?" Stiles asks off-handedly, and fuck, he'd never wanted to, had always wanted that layer between himself and his partners because for all that sex was intimate, he hadn't wanted that kind of intimacy. He'd wanted to get off, not to feel connected. But now, with Stiles, yes. He wants that. He wants all of it.

"Just fuck me," he bites out, and a grin blooms on Stiles' face, making him suddenly look softer, younger again. Stiles thrusts into him sharply and Derek nearly cries out. He wants to growl at Stiles for not taking the time to prep him, to finger him open and make him all loose and wet and grasping, but that's another perk of being a werewolf-the stretch burns for a few seconds, but he heals and grows accommodating within moments.

And then Stiles is fucking into him, hips pumping powerfully, and Derek swears his eyes are rolling back in his head. Derek feels spread wide open, his legs in the air as Stiles hooks his hands under Derek's knees, pushing back, opening him up a little more. Stiles stares down at where they join, the fascination evident in his eyes as he watches himself disappear into Derek time after time, bottoming out, his hips colliding rhythmically with Derek's ass as his hole stretches and spreads and takes Stiles' dick thrust after thrust. His gaze lifts to Derek's and whatever he sees has him leaning forward, bracing himself on his arms as he covers Derek's body with his own, still driving forward as Derek lifts his upper body to meet Stiles' lips. Stiles' tongue is in his mouth and Derek's hands are in his hair again-God, he'd wanted to do that the entirety of Stiles' junior year, after he'd grown it out and it was long enough to fist-and Derek can feel Stiles' cock slamming into him and creating a new, more intense pressure from the way Derek's abs are curled and tight with holding himself up.

"Jesus fuck, Derek, you feel so fucking good," Stiles pants harshly against his lips, and Derek agrees wholeheartedly. "In high school I fantasized about you fucking me, I never thought it would be the other way around. You were too alpha to let someone fuck you. But now you're letting me."

"I want to fuck you," Derek groans as Stiles' dick fills him repeatedly. "I'm _going_ to fuck you. But right now you need this."

Stiles stiffens, and at first Derek thinks it's because he's coming, but then he realizes it's because Stiles would never want to be perceived as needing anything. Before Stiles can pull back, in any way, Derek wraps one hand around the back of his neck and holds him, locking their gazes. "I'm giving you the control because for so long you've had to _take_ it. Let me give you something. Let me give you this."

Stiles lets out a shuddering moan as he straightens, pulling Derek's ass up on his thighs and working his hips frantically. Derek has his legs twined around Stiles' lower back and Stiles lets go of one thigh, reaching down to jack Derek's purpling dick. Precome streams from the head and down the shaft, coating it so Stiles' strokes are smooth and rapid. Derek can feel that aching, trembling sensation starting to spiral through him, from his toes up through his calves and thighs, and then sweat is beading on his forehead and his gasps are being ripped from his chest.

"Fuck, Stiles, I'm so fucking close," he pleads, and the awe on Stiles' face is heady.

"Come for me," he urges, fist tightening around Derek's cock. "Come apart under me, and all over me."

The words are intoxicating and Derek's head is swimming, and all he knows is the sensation of Stiles' dick slamming into his ass and the way his hole clutches and pulls at it greedily, and the feel of Stiles' fingers curling around his cock and yanking, tugging, coaxing, and then he's falling. He erupts, crying out as his back arches, thick ropes of pearly white jetting from his aching dick and splattering all over both of their chests. A few drops land on Stiles' chin and when he reaches up and wipes it away, sticking his fingers in his mouth to clean them, Derek's nearly-spent cock spurts another couple times before finally resting.

Stiles lets out a choked whine as he drives himself into Derek one last time, hips shuddering with the force of his release. Derek soaks in the warmth flooding him, reveling in the way Stiles collapses against his chest and curls against him, heedless of the mess between them. Their legs are tangled together as Stiles sprawls on top of him, panting and sated.

As they clear their way through the haze of pleasure, Stiles is still clinging to him, still nuzzling into his throat and there's the faint scent of tears, and Derek realizes how much Stiles needs him, yet will never admit to it. So he does it for him. "I'm staying this time, Stiles." It wasn't initially what he planned when he came back to Beacon Hills, but the second the words are out of his mouth, he knows that's exactly what he wants. He wants Stiles, he wants to protect him, he wants to be the one Stiles falls back on when the world gets to be too much and he needs someone to shelter him from the storm.

"Yeah?" Stiles' voice is rough, cracking, as he pulls back to stare at Derek with eyes clouded by a mix of hope and mistrust, and Derek brushes a kiss over his forehead.

"Yeah. I'm not leaving you again."

"Everyone else did," he mumbles, hands unconsciously clutching at Derek's shoulders, and Derek's heart breaks.

"I'm not everyone else," he promises. "You've been protecting this entire town for years. Lay down your sword, Stiles. Let me take it up for you."

Stiles sinks against him, and Derek can feel the sweep of his eyelashes against his own skin as Stiles' eyes close, can sense the slowing of his racing heart. "I wouldn't know how to let you," he sighs. "Just stand beside me, okay?"

"Always," Derek murmurs. "Go to sleep, Stiles. Rest. You've earned it." Stiles' arm slides over his waist and Derek lifts his other hand, lacing their fingers together. Stiles' tighten around him, reassuring himself that Derek isn't going anywhere, and Derek knows the exact second he slips into sleep.

It's the wee hours of the morning before he can stop watching the rise and fall of Stiles' chest, stop listening to the soft soughing of his breaths, and allow himself to follow.


End file.
